If that is the case, then I would support CptBadger's suggestion.
Maybe it could be done automatically with unworked tiles not affecting native relations.
If Col uses the same system as Civ4 then yes, only the civ who owns the tile via culture can work it.
It would be a great fix if that could be changed to allow native settlements to still work that land. Unless it is being worked by Euro (adding a significant diplo penalty) or bought out.
This was why I suggested Natives being able to spread culture, just so they can continue to use the land right beside their settlements, not necessarily so they can expand their territory (though I think it could make sense in the context of the game, given that nomadic peoples would use land far from their actual settlement). Having a minimum city border could work too. But if it could be changed so that natives could still work land that was culturally European, that would be the best system I think.
Real world examples of natives leaving their settlements to settle further away from Euros certainly do exist, I guess my issue is with the fact that the game's natives just give up their land with no real context as to why. If you're on good terms (pleased or above), and it's been a long enough period of time, maybe an event where you get some native converts (representing assimiliation)? If you're on bad terms, resettlement and have an additional diplomacy malus? Right now it seems very disconnected. In my current game the Caribs are annoyed with me, yet will give up one of their settlements if I ask (and then become cautious, as they have less border friction). Seems a little backwards that they should be angry that I've taken their land, but then give up a settlement to me for no payment and then be happier than they were before.
Sorry for any hostility on my part, I got really frustrated that after spending hours getting invested into this game that the natives still seemed to act so passively to everything!
To me the best part of Col is the choices you need to make as to the natives. Wiping them out is easy, but trying to coexist AND still trying to be the dominant Euro power is hard. I haven't felt the same level of reaction or hard decisions that are in original Col in this respect.
Also, how about an event where some of your colonists run away to "go native"
Thanks again